Effect of dopamine agonists and antagonists on DOPA formation in the substantia nigra.
The effect of different psychotropic drugs on the rate of DOPA accumulation after administration of a decarboxylase inhibitor (NSD 1015) was compared in the substantia nigra (SN) and caudate nucleus (CN) by a new radioenzymatic method. Inhibition of monoamine oxidase with pargyline or stimulation of dopamine (DA) receptors with apomorphine, N-n-propylnorapomorphine or D-amphetamine reduced DOPA formation in the CN and SN to the same extent. Vice versa, both inhibition of DA receptors with haloperidol or (-)sulpiride and depletion of DA concentration with reserpine enhanced DOPA formation to a greater extent in the CN than in the SN. Apomorphine antagonized not only the effect of haloperidol and (-)sulpiride, but also, and even more effectively, that of reserpine. The results indicate that DA synthesis in the SN is controlled by both end-product inhibition and DA receptor-mediated mechanisms.
D000818:Animals; D001058:Apomorphine / Q000494:pharmacology; D002421:Caudate Nucleus / Q000378:metabolism; D003913:Dextroamphetamine / Q000494:pharmacology; D004295:Dihydroxyphenylalanine / Q000378:metabolism*; D004298:Dopamine / Q000096:biosynthesis*; D006220:Haloperidol / Q000494:pharmacology; D008297:Male; D008996:Monoamine Oxidase Inhibitors / Q000378:metabolism; D010293:Pargyline / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000187:drug effects; D012110:Reserpine / Q000494:pharmacology; D013378:Substantia Nigra / Q000378:metabolism*; D013469:Sulpiride / Q000494:pharmacology
D008996:Monoamine Oxidase Inhibitors; D011954:Receptors, Dopamine; D004295:Dihydroxyphenylalanine; D013469:Sulpiride; D012110:Reserpine; D010293:Pargyline; D006220:Haloperidol; D001058:Apomorphine; D003913:Dextroamphetamine; D004298:Dopamine